FIG. 2.

ATM, but not ATR, is cleaved in HL60 cells induced to undergo apoptosis by any of a variety of agents and in apoptotic HeLa cells. (A) Cleavage of ATM during HL60 cell apoptosis induced by etoposide (68 μM for 4 h), staurosporin (5 μM for 4 h), bleomycin (100 μg/ml for 6 h), alcohol (5% for 4 h), or EGTA (5 mM for 5 h), as indicated. Nuclear extracts were prepared and 50 μg of protein was loaded per lane. (B) Cleavage of ATM but not ATR in HeLa cells treated with TNF-α (10 ng/ml) and cycloheximide (CHX; 20 μM) for the times shown. Nuclear extracts were prepared, and 50 μg of protein was loaded per lane.